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Projects chop gone awry

Discussion in 'The Hokey Ass Message Board' started by Last Hoorah, May 8, 2019.

  1. Last Hoorah
    Joined: Nov 13, 2009
    Posts: 102

    Last Hoorah

    My 2nd top chop on a model A, first went well on my coupe. My "30" sedan didn't. After cutting roof, "B" post on left came forward against door. Right side stayed in place.
    Body was bolted to frame, doors and everything was lined up prior to cutting.
    Had braces between "B" post and cowl. Nothing toward the back which probably caused the problem? "A" post or cowl didn't move.
    Would appreciate input on how to tackle this problem.
  2. Dave Mc
    Joined: Mar 8, 2011
    Posts: 1,754

    Dave Mc

    our pic`s 026.jpg our pic`s 022.jpg Tape measure and Bracing , measure diagonally as well as length .
    Last edited: May 8, 2019
    Hnstray likes this.
  3. I’ll bet it was a body shim issue and the cowl twisted and did move down. Assuming it’s a 2 door

    The cowl and doors move together.
    The quarter and B post move together.
    So if the door and B post are too close at the top then the cowl and quarter moved together at the top - sagged like a banana
    Hnstray and F&J like this.
  4. F&J
    Joined: Apr 5, 2007
    Posts: 13,135


    Without pics of the actual bracing before cutting, and also pics of what happened....

    My first thought is that the "bolted down" body was under stress on the left side due to wrong body shim blocks, or bent/swaybacked frame.

    If you use common sense, a body sitting on the frame, and if each body mount area did not move as you tightened each bolt, then that pillar could not jump forward.

    Did you notice any gaps between the middle area body blocks and frame, on the left side, before tightening those bolts? It would not have to be much of a gap at midpoint, to cause the upper part of the B to move a lot.
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  5. a boner
    Joined: Dec 25, 2004
    Posts: 4,882

    a boner

    With an almost 90 year old body.....shit happens!
    Good luck......hopefully it has to do with the body mounting shims.
  6. Hell, I'm only 66 and it's already happening to MY body....
  7. You can't have too much bracing when chopping a Model A sedan. HRP
    Dave Mc and 31Vicky with a hemi like this.
  8. Last Hoorah
    Joined: Nov 13, 2009
    Posts: 102

    Last Hoorah

    Don't remember if there was a gap at midpoint when I put the body on. The body could have had stress on it as I just put blocks between the body and frame. Every thing lined up ok so I didn't shim it. here are a couple pics of bracing and gap at door top and bottom. Have 1/4" gap at bottom and none at top.
    just trying to figure out at what point to start straightening the body. I guess put the top back on and see where it sits?
    chop2.png chop1.jpg
    Joined: Dec 14, 2009
    Posts: 1,655


    Is that flat bar going across from door to door?
    Flat bar does not have a lot of rididity (sp) to it when under stress from the sides as the diagonal bars could load it up.

    As has been stated the body could of been stressed at the mounts now causing this twist.
    I would try losening the body mounts or torquing them down little by little to see if the car “ springs” back
    Side to side and diagonal measurements are in your future by the bushel full.
    Good luck!

    I’m sure you said this more then once !
    31Vicky with a hemi likes this.
  10. alchemy
    Joined: Sep 27, 2002
    Posts: 13,567


    Fix the clearances before you weld anything.
    RICH B, F&J and 31Vicky with a hemi like this.
  11. Bed rail angle is not good for welding to. Nothing sticks very well or very long. It’s a MF to drill or saw cut too.
    The stuff makes great straight edges because it’s too damn hard for anything else.

    The Body envelope is kinda sturdy and might span gaps, but if you open the envelope by cutting the top off it’s sorta like jello.

    Get the shims right, bolts right and it will get a lot better on its own. Then you can play with pushing and proding
    0NE BAD 51 MERC and F&J like this.
  12. F&J
    Joined: Apr 5, 2007
    Posts: 13,135


    If you are positive that the frame is not swaybacked on the side... Then leave the roof off until you get that gap correct. See the body bolt that is close to the B pillar?, add shims under that mount until it is perfect. or you may need to also shim at the A pillar closest bolt.

    I always check the bare frame first. I use 4 foot bars across the frame rails every 2 or 3 feet. Then I sight down low to see if all the bars are level with each other, and if one part of one rail is low or high, you will never miss it as that bar will just look wrong.

    One other thing when shimming just one side: You don't want to end up with one B pillar bowed out, or in too far...this is where you dry fit the roof, then stand in back and front, sight down both sides of the body from every possible viewpoint.

    I always spend a lot of time on gaps, whether chopped or not, striving for perfect in the beginning. If you start with a "close enough" attitude in the very beginning, bad gaps will just make everything messed up the more you go... with welding or even patch panels, etc. Any extra hours will pay off with a finished good build.
  13. Last Hoorah
    Joined: Nov 13, 2009
    Posts: 102

    Last Hoorah

    Thanks guys for all your input. Going to try to check the frame and loosen all the body bolts and see what happens. I measured across between A&B post before and after and they stayed the same width.
    There is a 1/4" difference between the opening of the two doors. I'm Pretty sure B post came forward.
    Let you all know what I come up with.
  14. Then it fits just like before you cut it if it stayed the same
  15. Duke
    Joined: Mar 21, 2001
    Posts: 591


    My coupe b post moved in to the center when we cut the top off. A little push with a porta power and everything when together very nice. You could not see that the post moved, but the gap between the top and the post was large on one side.
  16. Hot Rods Ta Hell
    Joined: Apr 20, 2008
    Posts: 3,759

    Hot Rods Ta Hell

    Body may have had some preload which isn't uncommon. Once the roof was cut off it unloaded through your bracing.
    As everyone's mentioned, spend plenty of time getting things right before moving forward with the roof/chop work. Lots of measuring. Plumb bobs and a partner may be of some help here. A second set of eyes and hands (and moral support) may be just the ticket.

    I'd suggest lots of X bracing to hold things in place. For starters, run a brace from the top of the drivers B post to the base of the passenger B post and top of passenger B post to base of driver B post. (your bar running across at the B posts won't stop the body from leaning L or R whereas an X will).
    As you get things dialed in, zap in bracing without any preload (the bracing should merely "hold" the subject matter in place not "push" or "pull" the panel into place with a ton of force-like racking house framing) otherwise when the time comes to remove the internal bracing, it'll unwind and start stressing panels and weld joints. I see this mistake made on build TV shows where one guy has all his weight pushing a panel into place while his partner zaps it down with a mig flash. If a panel needs that much force, step back and make a relief cut and porta power it as Duke describes.
    Go slow and deliberate. She'll come back to you.

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